FIG. 1 depicts a known flatbed trailer 10 of the type typically used for transporting sod. A tarpaulin 12 is stored in a storage compartment 14 at the front of the trailer 10. The sod is loaded by forklift onto the loading surface 16 of the trailer 10. The tarpaulin 12 is then pulled manually rearwards from the storage compartment 14 across the uppermost portion of the sod pile. The tarpaulin 12 is then secured to the trailer 130 by elastic cords 18.
A principle disadvantage of known flatbed trailer enclosures, such as the enclosure shown in FIG. 1, is that the step of extending and securing the tarpaulin 12 to the trailer 10 is labour-intensive. The tarpaulin 12 must be pulled manually rearwards from the storage compartment 14 across the sod pile without damaging the sod. Once the tarpaulin 12 is fully extended, it must be secured to the flatbed trailer 10 through numerous elastic cords 18, while maintaining the tarpaulin 12 in position. Prior to unloading the sod, the elastic cords 18 must be removed and the tarpaulin 12 safely stored out of the way in the storage compartment 14 to avoid being damaged by the forklift.
Another disadvantage of known flatbed trailer enclosures is that the sod is not firmly held on the loading surface 16 of the flatbed trailer 10. As the tarpaulin 12 is only held in place by elastic cords 18, any lateral shifting of the sod on the flatbed trailer 10 can cause the elastic cords 18 to snap, and the sod to fall off the flatbed trailer 10. Similarly, any damage done to the tarpaulin 12 during the loading or unloading process can cause the tarpaulin 12 to tear, thereby allowing the sod or sod debris to fall off the flatbed trailer 10.
Various mechanisms for automatically enclosing trailers are known. Both U.S. Pat. No. 4,627,658 to Vold and U.S. Pat. No. 4,210,358 to Sweet teach an open-top trailer top-cover comprising a pair of panels rotatably mounted to the top of the trailer. Each panel is opened and closed by a rotating arm driven by a motor. However, the cost of adapting these implementations for the transportation of sod rolls on a flatbed trailer would be particularly high because a separate motor would be required for each panel. U.S. Pat. No. 5,498,057 to Reina teaches a retractable trailer cover comprising arch-like channels that support opposite ends of a tarpaulin, and a plurality of sprockets and endless chains for moving the tarpaulin, all driven by a single motor. Although cheaper to implement than a two-motor configuration, the single motor configuration disclosed by Reina would not allow both sides of the trailer cover to be closed simultaneously.
Accordingly, there remains a need for a flatbed trailer enclosure which is suitable for transporting sod.